Variable area fan nozzle with drive system health monitoring

ABSTRACT

A nacelle for a turbofan engine includes a variable area fan nozzle (VAFN) and a proximity sensor that is attached to a nacelle forward portion to sense the presence of the VAFN when stowed. The proximity sensor is not attached to the VAFN, thereby enabling the use of a proximity sensor such as linear variable displacement transformer having a relatively compact operational stroke.

BACKGROUND

Typical aircraft turbofan jet engines include an engine core, a nacellethat surrounds the engine core, and a fan that draws in a flow of airthat is split into bypass airflow and engine core airflow. The nacelleprovides a bypass duct that surrounds the engine core. The bypassairflow is transported through the bypass duct. The nacelle isconfigured to promote laminar flow of air through the bypass duct. Theengine core includes a multi-stage compressor to compress the enginecore airflow, a combustor to add thermal energy to the compressed enginecore airflow, and a turbine section downstream of the combustor toproduce mechanical power from the engine core airflow. The typicalturbine section has two and sometimes three turbine stages. The turbinestages are used to drive the compressor and the fan. After exiting fromthe turbine section, the engine core airflow exits through an exhaustnozzle at the aft end of the engine.

In a turbofan engine, the fan typically produces a majority of thethrust produced by the engine. The bypass airflow can be used to producereverse thrust typically used during landing. Thrust reversers mountedin the nacelle selectively reverse the direction of the bypass airflowto generate reverse thrust. During normal engine operation, the bypassairflow may or may not be mixed with the exhausted engine core airflowprior to exiting the engine assembly.

Several turbofan engine parameters have a significant impact upon engineperformance. Bypass ratio (BPR) is the ratio of the bypass airflow rateto the engine core airflow rate. A high BPR engine (e.g., BPR of 5 ormore) typically has better specific fuel consumption (SFC) and istypically quieter than a low BPR engine of equal thrust. In general, ahigher BPR results in lower average exhaust velocities and less jetnoise at a specific thrust. A turbofan engine's performance is alsoaffected by the engine's fan pressure ratio (FPR). FPR is the ratio ofthe air pressure at the engine's fan nozzle exit to the pressure of theair entering the fan. A lower FPR results in lower exhaust velocity andhigher propulsive efficiency. Reducing an engine's FPR can reach apractical limit, however, as a low FPR may not generate sufficientthrust and may cause engine fan stall, blade flutter, and/or compressorsurge under certain operating conditions.

One approach for optimizing the performance of an engine over variousflight conditions involves varying the fan nozzle exit area. Byselectively varying the fan nozzle's exit area, an engine's bypass flowcharacteristics can be adjusted to better match a particular flightcondition, for example, by optimizing the FPR relative to the particularthrust level being employed. Variable area fan nozzle (VAFN) systems,however, typically include multiple components that are selectivelyrepositioned relative to the nacelle via one or more actuation systems.

To satisfy operational, safety, and certification requirements (e.g.,Federal Aviation Administration requirements and European AviationSafety Agency requirements), a VAFN system must satisfy structuraldamage tolerance and system reliability requirements. To satisfy systemreliability requirements it may be necessary to monitor the VAFN systemto detect, for example, actuation system failures that may result indegraded aircraft performance such as increased drag and/or decreasedengine performance. Such monitoring, however, should be sufficientlyreliable, which may be difficult to achieve with VAFN systems havingmultiple components that are selectively repositioned relative to thenacelle via one or more actuation systems.

Accordingly, VAFN systems that employ reliable monitoring are desirable,especially where the monitoring is accomplished in a simple and costeffective manner.

BRIEF SUMMARY

The following presents a simplified summary of some embodiments of theinvention in order to provide a basic understanding of the invention.This summary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome embodiments of the invention in a simplified form as a prelude tothe more detailed description that is presented later.

Turbofan engine nacelles are disclosed that include a variable area fannozzle (VAFN) system having drive system health monitoring. In manyembodiments, the drive system health monitoring employs proximitysensors mounted to the engine nacelle to periodically verify thatpredetermined portions of a movable fan nozzle are positioned consistentwith a stowed configuration of the fan nozzle. By periodically verifying(e.g., twice per flight) the position of the predetermined portions ofthe fan nozzle, the required system reliability of the VAFN system canbe satisfied in a simple and cost effective manner.

Thus, in one aspect, a nacelle for a turbofan engine is provided. Thenacelle includes a nacelle forward portion, a sleeve, a fan nozzle, anda first proximity sensor attached to the nacelle forward portion. Thenacelle forward portion at least partially defines a bypass ductconfigured to transport bypass airflow of the engine. The nacelleforward portion has an aft edge that at least partially surrounds thebypass duct. The sleeve is movable disposed aft of the nacelle forwardportion aft edge and has a trailing edge. The sleeve is movable relativeto the nacelle forward portion between a forward position and an aftposition. The fan nozzle has a leading edge and a trailing edge. Aprimary flow exit for bypass airflow of the engine is partially definedby the fan nozzle trailing edge. The fan nozzle is disposed behind thesleeve trailing edge and movable relative to the sleeve between a stowedposition and a deployed position. The fan nozzle has a total range ofmotion relative to the nacelle forward portion between a forward-mostposition and an aft-most position. The forward-most position occurs whenthe sleeve is in the forward position and the fan nozzle is in thestowed position. The aft-most position occurs when the sleeve is in theaft position and the fan nozzle is in the deployed position. The totalrange of relative motion is divided into a first portion and a secondportion. The first proximity sensor is not attached to the fan nozzle orto the sleeve. The first proximity sensor generates a first signal thatis indicative of when the fan nozzle is in the first portion of thetotal range of relative motion and indicative of when the fan nozzle isnot in the first portion of the total range of relative motion. In manyembodiments, the first signal does not change in response to a change inthe position of the fan nozzle within the second portion of the totalrange of relative motion.

In many embodiments, a variable area fan nozzle (VAFN) port is definedbetween the sleeve trailing edge and the fan nozzle leading edge whenthe fan nozzle is in the deployed position. The VAFN port provides anadditional flow exit for bypass airflow of the engine flowing throughthe bypass duct other than the primary flow exit.

In many embodiments, a movement of the fan nozzle relative to thenacelle forward portion varies an exit area of the primary flow exit.For example, the fan nozzle and the nacelle forward portion cancooperate to define the primary flow exit such that moving the fannozzle relative to the nacelle forward portion varies the geometry ofthe primary flow exit so as to vary the exit area of the primary flowexit.

In many embodiments, the first proximity sensor includes a first memberand a second member that is movable relative to the first member. Thefirst member can have a fixed position relative to the nacelle forwardportion and the second member can interface with the fan nozzle onlywhen the fan nozzle is disposed within the first portion of the totalrange of relative motion. For example, the proximity sensor can includea linear variable differential transformer (LVDT) in which the secondmember (e.g., a plunger) is biased into an extended position relative tothe first member when the fan nozzle is not disposed within the firstportion of the total range of relative motion. In many embodiments, thefirst signal changes in response to a change in the position of the fannozzle relative to the nacelle forward portion within the first portionof the total range of relative motion. And the first proximity sensorcan be configured to accommodate variability in the position of theforward-most position relative to the nacelle forward position.

In many embodiments, the nacelle includes a second proximity sensor,which is also attached to the nacelle forward portion and not attachedto the fan nozzle. The second proximity sensor generates a second signalthat is indicative of when the fan nozzle is in the first portion of thetotal range of relative motion and indicative of when the fan nozzle isnot in the first portion of the total range of relative motion. Thenacelle can include a means to compare the first signal to the secondsignal, for example, to monitor for misalignment and/or defectivepositioning of the fan nozzle.

The nacelle can include a slave link (e.g., a slave plunger) mounted tothe sleeve. The slave link is movable relative to the sleeve andinterfaces with the fan nozzle only when the fan nozzle is disposedwithin the first portion of the total range of relative motion so as tocommunicate a position of the fan nozzle to the first proximity sensor.

In many embodiments, the nacelle includes a slave link assemblyconfigured to be detachably mounted to the sleeve. The slave linkassembly includes a slave plunger, a housing, and a spring (e.g., acompression spring). The housing is configured to be detachably mountedto the sleeve. The spring biases the slave plunger into an extendedconfiguration relative to the housing absent contact with the fannozzle. The slave plunger interfaces with the fan nozzle only when thefan nozzle is disposed within the first portion of the total range ofrelative motion so as to communicate a position of the fan nozzle to thefirst proximity sensor.

In many embodiments, the first portion of the total range of relativemotion is smaller than the second portion. For example, the firstportion can be less than 25% of the total range of relative motion. Thefirst portion can also be less than 10% of the total range of relativemotion. And the first portion can even be less than 5% of the totalrange of relative motion.

In many embodiments, the nacelle further includes a plurality of fannozzle actuators, a mechanical interconnection, a first configurationsensor generating a first configuration signal, a second configurationsensor generating a second configuration signal, and a means to comparethe first configuration signal to the second configuration signal. Thefan nozzle actuators are configured to selectively move the fan nozzlerelative to the sleeve between the stowed position and the deployedposition. The mechanical interconnection connects a drive source to thefan nozzle actuators to transfer an actuation motion from the drivesource to the fan nozzle actuators. The drive source actuates themechanical interconnection through a range of configurations between astowed configuration corresponding to the stowed position of the fannozzle and a deployed configuration corresponding to the deployedposition of the fan nozzle. The first configuration sensor generates afirst configuration signal indicative of the configuration of a firstlocation of the mechanical interconnection. The second configurationsensor generates a second configuration signal indicative of theconfiguration of a second location of the mechanical interconnection.The first and second configuration signals can be compared to, forexample, monitor for disconnects in the mechanical interconnectionbetween the first and second locations of the mechanicalinterconnection. In many embodiments, each of the first and secondconfigurations sensors includes a rotary variable differentialtransformer (RVDT).

In another aspect, a method is provided for monitoring a movable fannozzle of a turbofan engine. The method includes using a first proximitysensor, during a first time period when the fan nozzle is in a stowedposition relative to a movable sleeve of the turbofan engine and themovable sleeve is in a forward position relative to a nacelle forwardportion of the turbofan engine, to detect the presence of the firstportion of the fan nozzle. The first proximity sensor is attached to thenacelle forward portion and not attached to the fan nozzle or to thesleeve. A fan nozzle drive system operationally coupled with the fannozzle is actuated to move the fan nozzle relative to the sleeve fromthe stowed position to a deployed position. The fan nozzle drive systemis actuated to return the fan nozzle from the deployed position to thestowed position. A sleeve drive system operationally coupled with thesleeve is actuated to move the sleeve and the fan nozzle relative to thenacelle forward portion thereby moving the sleeve from a forwardposition to an aft position relative to the nacelle forward portion. Thesleeve drive system is actuated to return the sleeve from the aftposition to the forward position. During a second time period afterreturning the fan nozzle to the stowed position and after returning thesleeve to the forward position, the first proximity sensor is used todetect the presence of the first portion of the fan nozzle.

In many embodiments, the method for monitoring a movable fan nozzleincludes using a second proximity sensor to detect the presence of asecond portion of the fan nozzle. The second proximity sensor isattached to the nacelle forward portion and not attached to the fannozzle or to the sleeve. In many embodiments, a first signal generatedby the first proximity sensor is compared with a second signal generatedby the second proximity sensor to, for example, monitor for misalignmentand/or defective positioning of the fan nozzle.

In many embodiments, the first proximity sensor used in the method formonitoring a movable fan nozzle includes a first member and a secondmember that is movable relative to the first member. For example, themethod can include supporting the first member of the first proximitysensor in a fixed position relative to the nacelle forward portion.Relative motion between the fan nozzle and the nacelle forward portionis used to articulate the second member relative to the first memberonly during a subset of a total range of relative motion between the fannozzle and the nacelle forward portion. In many embodiments, the subsetis less than 25% of the total range of relative motion. The method caninclude generating a first signal indicative of a position of the secondmember relative to the first member.

In many embodiments, the method for monitoring a movable fan nozzle usesa slave link supported by a sleeve of the turbofan engine to communicatea movement of the fan nozzle to the second member of the first proximitysensor. The sleeve is movable relative to the nacelle forward portionbetween a forward position and an aft position. And the fan nozzle ismovable relative to the sleeve between a stowed configuration and adeployed position.

In many embodiments, the method for monitoring a movable fan nozzleincludes transferring an actuation motion from a drive source through amechanical interconnection to a plurality of fan nozzle actuatorsoperatively coupled with the fan nozzle. The method can further includegenerating a first configuration signal indicative of the configurationof the mechanical interconnection at a first location, generating asecond configuration signal indicative of the configuration of themechanical interconnection at a second location, and comparing the firstand second configuration signals to monitor the mechanicalinterconnection (e.g., for malfunctions). And the method can furtherinclude comparing a first signal generated by the first proximity sensorwith at least one of the first configuration signal or the secondconfiguration signal to monitor the fan nozzle drive system downstreamof at least one of the first location or the second location.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the ensuing detailed descriptionand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustration of a turbofan engine thatincludes a variable area fan nozzle (VAFN) assembly, in accordance withmany embodiments.

FIG. 2 is a cross-sectional view of the turbofan engine of FIG. 1.

FIG. 3 is an end view of the turbofan engine of FIG. 1.

FIG. 4 is a perspective view that shows a portion of the VAFN assemblyof the turbofan engine of FIG. 1.

FIG. 5 is another perspective view that shows a portion of the VAFNassembly of the turbofan engine of FIG. 1.

FIG. 6 is a schematic diagram showing a VAFN system that includes linearvariable differential transformers (LVDTs) connected between a nacelleforward portion and VAFNs to monitor the positions of the VAFNs, inaccordance with many embodiments.

FIG. 7 is a schematic diagram showing a VAFN system that includes LVDTsconnected between translating thrust reverser sleeves and VAFNs tomonitor the positions of the VAFNs, in accordance with many embodiments.

FIG. 8 is a schematic diagram showing a VAFN system that includes LVDTsattached to a nacelle forward portion to monitor the positions of VAFNs,in accordance with many embodiments.

FIG. 9 is a perspective view showing a spring-type LVDT mounted to aforward nacelle portion, a spring-loaded slave link supported by athrust reverser sleeve fitting, and a VAFN fitting contacting the slavelink, in accordance with many embodiments.

FIGS. 10A and 10B are perspective views illustrating a spring-loadedslave link assembly configured to be detachably mounted to a thrustreverser sleeve fitting, in accordance with many embodiments.

FIG. 11A is a perspective view illustrating the spring-loaded slave linkassembly of FIGS. 10A and 10B mounted in a thrust reverse sleeve fittingwith the VAFN in a deployed position, in accordance with manyembodiments.

FIG. 11B is a perspective view illustrating the spring-loaded slave linkassembly of

FIGS. 10A and 10B mounted in a thrust reverse sleeve fitting with theVAFN in a stowed position, in accordance with many embodiments.

FIGS. 12A, 12B, and 12C schematically illustrate a turbofan enginenacelle that includes proximity sensors mounted to a forward nacelleportion that directly interface with a VAFN when the VAFN is in a stowedconfiguration, in accordance with many embodiments.

FIG. 13 is a simplified diagram showing acts of a method for monitoringa VAFN of a turbofan engine, in accordance with many embodiments.

FIG. 14 is a simplified diagram showing optional acts that can beaccomplished in the method of FIG. 13, in accordance with manyembodiments.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention can be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1 shows aturbofan engine 10 that includes a variable area fan nozzle (VAFN)assembly 12 having a translating fan nozzle 50 that can be selectivelyadjusted, for example, as the engine 10 operates under different flightconditions. As discussed above, such an adjustment can be used tooptimize the engine's performance. As shown in FIG. 2, the translatingfan nozzle 50 can be selectively translated (i.e., moved fore and aft)to vary the fan nozzle's exit area 52 and to adjust how much of thebypass airflow exits through an upstream exit 60 formed by the VAFNassembly 12. For example, when the translating fan nozzle 50 is in thestowed position, the upstream exit 60 is closed and the exit area 52 isminimized, thereby maximizing the fan pressure ratio (FPR) for aparticular operational condition. And when the translating fan nozzle 50is in the fully deployed position, the upstream exit 60 opening ismaximized and the exit area 52 is maximized, thereby minimizing the FPRfor the particular operational condition. Accordingly, selectivelypositioning the translating fan nozzle 50 can be used to selectivelyvary the FPR. And varying the FPR can be used to optimize engineperformance, increase fan stall margins, avoid engine malfunction,and/or avoid engine shutdown. For purposes of illustration, the VAFNassembly 12 is shown in the context of a turbofan aircraft engine 10.The engine 10 can be mounted to a wing or fuselage of an aircraft, forexample, by a pylon or other similar support (not shown in the figures).

The engine 10 includes an engine core 16 and a nacelle 18. The enginecore 16 is housed in a core cowl 19. As shown in FIG. 2, a fan 20 ismounted adjacent to an upstream end of the nacelle 18, and includes aseries of fan blades 22 that are rotated about the engine centerline CLduring engine operation so as to draw a flow of air into an inlet end 26of the engine 10. An annular bypass duct 24 is defined between theengine core 16 and the nacelle 18. The airflow drawn into the engine 10is accelerated by the rotating fan blades 22. A portion of the airflowis directed into and through a multi-stage compressor (not illustrated)within the engine core 16. The engine core airflow through the enginecore 16 is initially passed through the compressor to increase theairflow pressure, after which the pressurized air is passed through acombustor (not shown), where it is mixed with fuel and the mixtureignited. The combustion of the fuel and air mixture within the combustorcauses the air to expand, which in turn drives a series of turbines atthe rear of the engine, indicated generally at 38, to rotate and in turnto provide power to the fan 20.

The bypass airflow accelerated by the rotating fan blades 22 passesthrough the bypass duct 24, past stators 40, and out through the nozzleassembly 12. The fan 20 produces most of the engine thrust. The highpressure heated exhaust gases from the combustion of the fuel and airmixture are directed out of the rear of the engine core 16 downstream ofthe turbine section 38.

The translating fan nozzle 50 can include a ring-like annular airfoilstructure mounted at the trailing end of a thrust reverser 80, adjacentto and circumscribing the engine core cowl 19. The area between thetrailing edge of the translating fan nozzle 50 and the core cowl 19defines the nozzle exit area 52 for the translating fan nozzle 12. Asshown in FIG. 1 and FIG. 3, the translating fan nozzle 50 includes anarcuate first ring section 54 and an arcuate second ring section 56.Each ring section 54, 56 is axially translatable in the direction of thebidirectional arrow 58. Translation of the fan nozzle 50 effects adesired size of the upstream exit 60 and varies the outlet geometry andexit area 52 of the fan nozzle 12 outlet for the engine bypass airflow.The fan nozzle 50 can be translated, for example, by a plurality of ringactuators 70.

The thrust reverser 80 is adjacent to and forward of the translating fannozzle 50 to block and redirect the bypass airflow in the bypass duct 24into a thrust reversing vector. In FIG. 1, the thrust reverser 80 andthe translating fan nozzle 50 are in stowed (closed) positions. Thethrust reverser 80 includes an arcuate first sleeve (cowl) section 82and an opposed arcuate second sleeve (cowl) section 84 (shown in FIG.3). The thrust reverser sleeve sections 82, 84 are axially translatablein the direction of the bidirectional arrow 86 by a plurality of sleeveactuators 90. The thrust reverser sleeve sections 82, 84 aretranslatable over a series of cascade vanes 88. The cascade vanes 88 areindicated by dashed lead lines in FIG. 1 because they are not visiblewhen the thrust reverser 80 is in the stowed position. Axial translationof the sleeve sections 82, 84 in the fore and aft directions allows thebypass airflow to pass through the cascade vanes 88 to generate athrust-reversing vector.

FIG. 3 is a cross-sectional view of the aft end of the engine 10, andillustrates the arrangement of the ring and sleeve actuators 70, 90,respectively, around the periphery of the engine 10. As shown in FIG. 1,and more clearly in FIG. 3, the sleeve half section 82 and the ringsection 54 cooperate to generally define an approximately 180 degreesector of the combined thrust reverser and translating fan nozzle.Likewise, sleeve half section 84 and ring half section 56 cooperate togenerally define an opposed approximately 180 degree sector of thethrust reverser and translating fan nozzle. Together, these approximate180 degree sectors cooperate to define the entire approximate 360 degreethrust reverser and translating fan nozzle.

As shown in FIGS. 1-3, each thrust reverser sleeve half-section 82, 84of the thrust reverser 80 is translated by one or more (three are shown)peripherally-spaced sleeve actuators 90 fixedly mounted on the nacelle18. In the embodiment shown, three actuators 90 are used for each sleevehalf-section 82, 84. Each ring section 54, 56 of the translating fannozzle 50 similarly is translated by one or more (three are shown)peripherally-spaced ring actuators 70. Ring actuators 70 can be mountedon an adjacent thrust reverser sleeve section 82, 84, respectively. Thering actuators 70 can be powered by, for example, electricity,mechanical means, pneumatics, hydraulics, or other suitable means, withappropriate power cables and conduits (not shown) passing viapre-defined passages between or above the thrust reverser cascade boxesor pivot doors. The number and arrangement of ring and sleeve actuators70, 90 can be varied, for example, according to the thrust reverser andtranslating fan nozzle configuration, and according to other factors.The ring sections 54, 56 may be mounted in, for example, upper and lowerguide structures 102 located at each end of corresponding sleevesections 82, 84, respectively. Guide tubes 104 may be mounted in thenacelle 18 and may extend into the ring sections 54, 56 to stabilize thering sections 54, 56 against undesirable translation and/or vibration.Guide tubes can alternatively be mounted in the thrust reverser 80.

The translating fan nozzle 50 can be a continuous (e.g., one-piece) or,as shown in FIG. 3, a continuing (e.g., split or multi-section)generally annular ring having an airfoil cross section. Accordingly, theupstream exit 60 (formed when the translating fan nozzle 50 moves in theaft direction away from the sleeve sections 82, 84) can have the form ofa generally annular gap extending around the perimeter of the rear ofthe nacelle 18. Other outlet shapes can also be used, for example, oval,etc. The generally annular gap between the ring sections 54, 56 and thesleeve sections 82, 84 can be continuous, for example, or interrupted atone or more locations, such as, for example, at points of bifurcation orother separation of the translating fan nozzle 50. The bypass duct 24may also be interrupted at one or more locations.

The translating fan nozzle 50 and surrounding structure are describedbelow with reference to FIG. 4 and FIG. 5. In FIG. 4 and FIG. 5,elements that are obscured or partially obscured due to interveningelements are indicated by dashed lead lines.

FIG. 4 is a partial view of the mounting structure for a first ringsection 54 of the translating fan nozzle 50 and the corresponding,adjacent first sleeve section 82 of the thrust reverser 80. The secondring section 56 of the translating fan nozzle 50 and the second sleevesection 84 of the thrust reverser 80, which are shown in FIG. 1 and FIG.3, can be mounted in a similar manner. In FIG. 4, the thrust reverser 80is in a stowed position, covering the cascade vanes 88. The translatingfan nozzle 50 is in an open or deployed position so that an upstreamexit 60 is defined between the first ring section 54 and the firstsleeve section 82. The rearward axial translation of the first ringsection 54 to the deployed position is indicated by the arrow A. Thering actuators 70 can extend from the sleeve section 82, across theupstream exit 60, and connect to a fore end of the ring section 54. Theguide tubes 104 can also extend from the sleeve section 82, across theupstream exit 60, and connect to the fore end of the ring section 54. Asleeve actuation cable 96 can connect to each sleeve actuator 90 toprovide simultaneous actuation of each actuator 90.

FIG. 5 shows the thrust reverser 80 in a deployed position and thetranslating fan nozzle 50 in the open position. The rearward axialtranslation of the first sleeve section 82 from the position shown inFIG. 4 to the deployed position is indicated by the arrow B. Rearwardtranslation of the sleeve section 82 exposes the cascade vanes 88 duringoperation of the thrust reverser 80. The ring section 54 can also betranslated aft during operation of the thrust reverser 80, as shown inthis embodiment. The ring section 54 may be deployed at the same timethat the thrust reverser 80 is deployed, or they may be deployed atdifferent times.

FIG. 6 is a schematic diagram of a VAFN actuation system 200 thatincorporates a plurality of VAFN actuators 270, in accordance with manyembodiments. The actuation system 200 can be used in the turbofan engine10 having the cascade-type thrust reverser 80 as described herein, andto translate one or more fan nozzle segments 54, 56 between their stowedand deployed positions. In the VAFN actuation system 200, the pair oftranslating thrust reverser sleeve sections 82, 84 are movably disposedaft of the nacelle 18, and the pair of translating fan nozzle segments54, 56 are movably disposed aft of the sleeve sections 82, 84. Each fannozzle segment 54, 56 is positioned in its stowed and deployed positionsby the VAFN actuators 270. Each VAFN actuator 270 can include a gear box271, a telescoping coupling 273 having a non-translating portion 273 aand a translating portion 273 b, an inline coupling 274, and anextensible portion 277 having an extensible sleeve 277 b. Thetelescoping coupling 273 permits fore and aft movement of the thrustreverser sleeve sections 82, 84 while maintaining rotational engagementbetween the gear box 271 and the inline coupling 274. The longitudinalaxes of the telescoping coupling 273 and the extensible portion 277 areaxially aligned, and the coupling 273 and extensible portion 277 aredirectly connected together without any intervening gears ortransmission. Accordingly, the rotational speed and/or output torqueprovided to the extensible portion 277 by the inline coupling 274 issubstantially the same as the rotational speed and/or torque provided tothe coupling 274 by the gear box 271 and the telescoping coupling 273.

As shown in FIG. 6, the VAFN actuators 270 are connected to a powerdrive unit (PDU) 210. Flexible drive shafts 203 rotatably connectadjacent gear boxes 271 to the PDU 210. And flexible transmission shafts205 rotatably connect non-adjacent gear boxes 271 to the PDU 210. ThePDU 210 includes a power gear box 212 driven by a motor 214. Whenactuated, the PDU 210 drives the shafts 203, 205 and interconnected gearboxes 271, thereby simultaneously actuating the VAFN actuators 270 andeffecting desired simultaneous movement of the fan nozzle segments 54,56 in a forward or aft direction. The non-translating portion 273 a andthe movable portion 273 b of the actuators 270 can be rotatably coupledtogether by a suitable splined coupling configured to allow relativetranslation between the rotationally coupled components.

FIG. 6 also shows a schematic representation of a control system for theVAFN actuation system 200. In the embodiment shown, linear variabledisplacement transducers (LVDTs) 220 are connected at one end to thenacelle 18 and at the other end to the fan nozzle segments 54, 56. TheLVDTs 220 detect the positions of the fan nozzle segments 54, 56relative to the nacelle 18. The LVDTs 220 can be connected to anautomatic control system 299 that controls operation of the PDU 210. Forexample, the LVDTs 220 can be operably connected to a Full AuthorityDigital Engine Control (FADEC) system. Inputs from the LVDTs 220 can beused by the control system 299 to monitor the position of the fan nozzlesegments 54, 56, and to control operation of the PDU 210 accordingly.The positional monitoring provided by the LVDTs can also be accountedfor to demonstrate compliance with overall VAFN system operational andreliability requirements. Alternatively or in addition, the PDU 210 canbe equipped with one or more rotary variable displacement transformers(RVDTs) 201 to detect when predetermined rotational displacement limitsfor the PDU 210 have been reached.

The LVDTs 220, however, must be long enough to accommodate the totalstroke of the fan nozzle segments 54, 56 relative to the nacelle 18. Oneapproach for reducing the size of the LVDTs used to monitor the fannozzle segments 54, 56 is to couple the LVDTs between the thrustreverser sleeve sections 82, 84 and the fan nozzle segments 54, 56.

FIG. 7 is a schematic diagram of a VAFN actuation system 300 thatincorporates a plurality of VAFN actuators 370 that are connectedbetween the thrust reverser sleeve sections 82, 84 and the fan nozzlesegments 54, 56, in accordance with many embodiments. The actuationsystem 300 can be used in the turbofan engine 10 having the cascade-typethrust reverser 80 as described herein, and to translate one or more fannozzle segments 54, 56 between their stowed and deployed positions. Inthe VAFN actuation system 300, the pair of translating thrust reversersleeve sections 82, 84 are movably disposed aft of the nacelle 18, andthe pair of translating fan nozzle segments 54, 56 are movably disposedaft of the sleeve sections 82, 84. Each fan nozzle segment 54, 56 ispositioned in its stowed and deployed positions by the VAFN actuators370. Each VAFN actuator 370 can include a gear box 371, a telescopingcoupling 373, universal joints 375, and a steady bearing 377. Thetelescoping coupling 373 permits fore and aft movement of the thrustreverser sleeve sections 82, 84 relative to the nacelle forward portion18.

As shown in FIG. 7, the VAFN actuators 370 can be connected to a powerdrive unit (PDU) 310. Flexible drive shafts 303 and upper drive shafts305 can rotatably connect the gear boxes 371 to the PDU 310. Whenactuated, the PDU 310 drives the shafts 303, 305 and interconnected gearboxes 371, thereby simultaneously actuating the VAFN actuators 370 andeffecting desired simultaneous movement of the fan nozzle segments 54,56 in a forward or aft direction.

FIG. 7 also shows a schematic representation of a control system for theVAFN actuation system 300. In the embodiment shown, each of the LVDTs320 are connected at one end to one of the thrust reverser sleevesections 82, 84 and at the other end to one of the fan nozzle segment54, 56. The LVDTs 320 detect the positions of the fan nozzle segments54, 56 relative to the thrust reverser sleeve sections 82, 84. The LVDTs320 can be connected to an automatic control system 399 that controlsoperation of the PDU 210. For example, the LVDTs 320 can be operablyconnected to a Full Authority Digital Engine Control (FADEC) system.Inputs from the LVDTs 320 can be used by the control system 399 tomonitor the position of the fan nozzle segments 54, 56, and to controloperation of the PDU 310 accordingly. The positional monitoring providedby the LVDTs 320 can also be accounted for to demonstrate compliancewith overall VAFN system operational and reliability requirements.Alternatively or in addition, the PDU 310 can be equipped with one ormore motor sensors 380 (e.g., rotary variable displacement transformers(RVDTs)) to detect when predetermined rotational displacement limits forthe PDU 310 have been reached.

To accommodate the relative motion between the translating thrustreverser sleeve sections 82, 84 and the nacelle 18, the VAFN actuationsystem 300 also includes telescoping wiring harness assemblies 382 toelectrically connect the LVDTs 320 to the automatic control system 399.Other connection devices may also be used.

FIG. 8 is a schematic diagram of a VAFN actuation system 400 thatincorporates a plurality of VAFN actuators 470 that are connectedbetween the thrust reverser sleeve sections 82, 84 and the fan nozzlesegments 54, 56, in accordance with many embodiments. The actuationsystem 400 can be used in the turbofan engine 10 having the cascade-typethrust reverser 80 as described herein, and to translate one or more fannozzle segments 54, 56 between their stowed and deployed positions. Inthe VAFN actuation system 400, the pair of translating thrust reversersleeve sections 82, 84 are movably disposed aft of the nacelle 18, andthe pair of translating fan nozzle segments 54, 56 are movably disposedaft of the sleeve sections 82, 84. Each fan nozzle segment 54, 56 ispositioned in its stowed and deployed positions by the VAFN actuators470. Each VAFN actuator 470 can include a gear box 471, a telescopingcoupling 473, universal joints 475, and a steady bearing 477. Thetelescoping coupling 473 permits fore and aft movement of the thrustreverser sleeve sections 82, 84 relative to the nacelle forward portion18.

As shown in FIG. 8, the VAFN actuators 470 can be connected to a powerdrive unit (PDU) 410. The PDU 410 includes two electric motors 412, twobrakes 414, and a differential 416. Each of the electric motors 412 isconnected with one of the brakes 414. The differential 416 receivesinput from both of the electric motors 412 and produces an output usedto drive the VAFN actuators 470. Flexible drive shafts 403 and upperdrive shafts 405 rotatably connect the gear boxes 471 to the PDU 410. Toactuate the translating fan nozzle segments 54, 56, the PDU 410 drivesthe shafts 403, 405 and interconnected gear boxes 471, therebysimultaneously actuating the VAFN actuators 470 and effecting desiredsimultaneous movement of the fan nozzle segments 54, 56 in a forward oraft direction.

FIG. 8 also shows a schematic representation of a control system for theVAFN actuation system 400. In the embodiment shown, LVDTs 420 areattached to the forward nacelle portion 18 and are not attached to thefan nozzle segments 54, 56. The LVDTs 420 are also not attached to thethrust reverser sleeve sections 82, 84. Instead, the LVDTs 420 are of aspring-loaded type in which a plunger shaft 422 is contacted by arespective one of the fan nozzle segments 54, 56 when the fan nozzlesegment is within a corresponding forward portion of the total range ofmotion of the fan nozzle segments 54, 56 relative to the nacelle forwardportion 18, for example, when both the thrust reverser sleeve sections82, 84 and the fan nozzle segments 54, 56 are in forward-most (stowed)positions relative to the forward nacelle portion 18. When the fannozzle segments 54, 56 are disposed sufficiently aft relative to theforward nacelle portion 18 the plunger shaft 422 is not in contact withits respective fan nozzle segments 54, 56. By not attaching the LVDTs420 to the fan nozzle segments 54, 56 or to the thrust reverser sleevesections 82, 84, the LVDTs 420 can have a relatively small operationalstroke that is not constrained by the total relative movement betweenthe fan nozzle segments 54, 56 and the forward nacelle portion 18 or bythe total relative movement between the fan nozzle segments 54, 56 andthe thrust reverser sleeve sections 82, 84. In many embodiments, theoperational stroke of the LVDTs 420 is selected to be significantlysmaller than the total relative movement between the fan nozzle segments54, 56 and the forward nacelle portion 18. For example, in manyembodiments, the operational stroke of the LVDTs 420 is less than 25% ofthe total relative movement between the fan nozzle segments 54, 56 andthe forward nacelle portion 18. In many embodiments, the operationalstroke of the LVDTs 420 is less than 10% of the total relative movementbetween the fan nozzle segments 54, 56 and the forward nacelle portion18. And in many embodiments, the operational stroke of the LVDTs 420 isless than 5% of the total relative movement between the fan nozzlesegments 54, 56 and the forward nacelle portion 18.

The LVDTs 420 can be connected to an automatic control system 499 thatcontrols operation of the PDU 410. For example, the LVDTs 420 can beoperably connected to a Full Authority Digital Engine Control (FADEC)system. Inputs from the LVDTs 420 can be used by the control system 499to determine when the fan nozzle segments 54, 56 are in their fullystowed or fully deployed positions, for example, and to controloperation of the PDU 410 accordingly. The positional monitoring providedby the LVDTs 420 can also be accounted for to demonstrate compliancewith overall VAFN system reliability requirements.

The VAFN actuation system 400 also includes two dual channel RVDTs 424to provide monitoring of the actuation of the fan nozzle segments 54,56. Each of the RVDTs 424 is operationally coupled with one of the gearboxes 471. The RVDTs 424 are disposed downstream of the flexible driveshafts 403. Each of the RVDTs 424 monitors rotation of its correspondinggear box 471. Each of the RVDTs 424 generates two signals (Channel Asignal 426 and Channel B signal 428) indicative of the rotationalposition of the monitored gear box. The signals 426, 428 arecommunicated to the FADEC system and are used by the FADEC system tomonitor the position of the fan nozzle segments 54, 56, and to monitorfor any incompatibility between the signals 426, 428, which can be causeby, for example, a mechanical malfunction such as a broken flexibledrive shaft 403. The use of dual channel RVDTs provides systemredundancy that may enable the ability to dispatch an airplane with oneinoperative channel.

FIG. 9 is a perspective view showing one of the spring-type LVDTs 420mounted to the forward nacelle portion 18, a spring-loaded slave plungerhaving an aft end 430 a and a forward end 430 b supported by a thrustreverser sleeve fitting 432, and a VAFN fitting 434 contacting the slaveplunger aft end 430 a, in accordance with many embodiments. In theembodiment shown, the slave plunger aft end 430 a is contacted by theVAFN fitting 434. In turn, the slave plunger forward end 430 b contactsa plunger shaft 436 of the LVDT 420 and thereby the slave plungercommunicates the position of the VAFN fitting 434 to the LVDT 420. Theslave plunger is spring loaded and is constrained to translate along aline of action by the thrust reverser sleeve fitting 432. When the VAFNsegments 54, 56 are disposed sufficiently aft from their stowedpositions, a gap occurs between the slave plunger aft end 430 a and theVAFN fitting 434. The spring-loaded slave plunger and the plunger 436 ofthe LVDT 420 are spring biased into an aft extended position so as to bepositioned for detecting when the fan nozzle segments 54, 56 arereturned to their stowed positions. The use of the spring-loaded slaveplunger enables increased flexibility in the configuration of the thrustreverser sleeve sections 82, 84 by allowing structural elements of thethrust reverser sleeve sections 82, 84, such as the thrust reversersleeve fitting 432 to be disposed between the LVDTs 420 and thelocations on the fan nozzle segments 54, 56 used to drive the plunger436 of the LVDT 420.

FIGS. 10A and 10B are perspective views illustrating a spring-loadedslave link assembly 450 configured to be detachably mounted to a thrustreverser sleeve fitting, in accordance with many embodiments. Theassembly 450 provides a self-contained, easily replaceable unit that canbe installed into a mounting hole in the thrust reverse sleeve fittingso as to provide a slave plunger 430 for communicating the position ofthe VAFN fitting 434 to the LVDT 420. The assembly 450 includes theslave plunger 430, a housing 452, an end cap 454, and compression spring456 that interfaces with the end cap 454 and the slave plunger 430 tobias the slave plunger 430 into an extended configuration (shown in FIG.10A) absent contact with the VAFN fitting 434. FIG. 10B shows theassembly 450 in a configuration corresponding to the nominal stowedposition of the fan nozzle segments 54, 56. As illustrated, the assembly450 is configured to allow an additional 0.40 inch stroke of the slaveplunger 430, thereby allowing for variability in the stowed position ofthe fan nozzle segments 54, 56 relative to the nacelle forward portion18. FIG. 11A is a perspective view illustrating the spring-loaded slaveplunger assembly 450 mounted in the thrust reverse sleeve fitting 432with the fan nozzle segments 54, 56 in a deployed position. And FIG. 11Bis a perspective view illustrating the spring-loaded slave plungerassembly 450 mounted in the thrust reverse sleeve fitting 432 with thefan nozzle segments 54, 56 in the stowed position.

In many embodiments, one or more and even all of the LVDTs 420 can beconfigured and mounted to directly interface with the fan nozzlesegments 54, 56 without the use of a slave link. FIGS. 12A, 12B, and 12Cschematically illustrate a turbofan engine nacelle that includesproximity sensors mounted to the forward nacelle portion 18. Theproximity sensors (e.g. LVDTs 420) directly sense the presence of thefan nozzle segment 54 when the fan nozzle segment 54 is in the stowedposition (as illustrated in FIG. 12A). FIG. 12B illustrates clearancebetween the plungers 436 of the LVDTs 420 when both the fan nozzlesegment 54 and the thrust reverse sleeve section 82 are in deployedpositions. And FIG. 12C illustrates clearance between the plungers 436of the LVDTs 420 when the fan nozzle segment 54 is deployed and thethrust reverse sleeve section 82 is stowed.

FIG. 13 is a simplified diagram showing acts of a method 500 formonitoring a variable area fan nozzle of a turbofan engine, inaccordance with many embodiments. The nacelles, systems, and assembliesdescribed herein can be used to perform the method 500. In act 502,during a first time period when a fan nozzle is in a stowed positionrelative to a movable sleeve of the engine and the sleeve is in aforward position relative to a nacelle forward portion of the engine, afirst proximity sensor is used to detect the presence of the firstportion of the fan nozzle (e.g., one end of the fan nozzle). The firstproximity sensor is attached to the nacelle forward portion. The firstproximity sensor is not attached to the fan nozzle. In act 504, a fannozzle drive system that is operationally coupled with the fan nozzle isactuated to move the fan nozzle relative to the sleeve from the stowedposition to a deployed position. In act 506, the fan nozzle drive systemis actuated to return the fan nozzle from the deployed position to thestowed position. In act 508, a sleeve drive system that is operationallycoupled with the sleeve is actuated to move the sleeve and the fannozzle relative to the nacelle forward portion thereby moving the sleevefrom a forward position to an aft position relative to the nacelleforward portion. In act 510, the sleeve drive system is actuated toreturn the sleeve from the aft position to the forward position. And inact 512, during a second time period subsequent to returning the fannozzle to the stowed position and subsequent to returning the sleeve tothe forward position, the first proximity sensor is used to detect thepresence of the first portion of the fan nozzle.

FIG. 14 is a simplified diagram showing optional acts that can beaccomplished in the method 500, in accordance with many embodiments. Inact 514, a second proximity sensor is used to detect the presence of asecond portion of the fan nozzle (e.g., the second portion beingdifferent from the first portion). The second proximity sensor isattached to the nacelle forward portion. The second proximity sensor isnot attached to the fan nozzle. In act 516, a first signal generated bythe first proximity sensor is compared with a second signal generated bya second proximity sensor to monitor for misalignment and/or defectivepositioning of the fan nozzle. For example, unbalanced articulation ofthe fan nozzle can cause the fan nozzle to become misaligned and/ordefectively positioned relative to the thrust reverser sleeve and/or thenacelle forward portion. In act 518, a first member of the firstproximity sensor is supported in a fixed position relative to thenacelle forward portion. In act 520, motion of the fan nozzle relativeto the nacelle forward portion is used to articulate a second member ofthe first proximity sensor relative to the first member only during asubset of the total range of motion between the fan nozzle and thenacelle forward portion. In many embodiments, the subset is less than25% of the total range of relative motion between the fan nozzle and thenacelle forward portion. The subset can be less than 10% of the totalrange of relative motion between the fan nozzle and the nacelle forwardportion. And the subset can be less than 5% of the total range ofrelative motion between the fan nozzle and the nacelle forward portion.In act 522, a first signal indicative of a position of the second memberrelative to the first member is generated. In act 524, a slave linksupported by the sleeve is used to communicate a movement of the fannozzle to the second member of the first proximity sensor In act 526, anactuation motion is transferred from a drive source through a mechanicalinterconnection to a plurality of fan nozzle actuators operativelycoupled with the fan nozzle. In act 528, a first configuration signal isgenerated that is indicative of a configuration of the mechanicalinterconnection at a first location, for example, via an RVDT toindicate a particular rotational configuration of a range of rotationalconfigurations used to position the fan nozzle. In act 530, a secondconfiguration signal is generated that is indicative of a configurationof the mechanical interconnection at a second location. In act 532, thefirst and second configuration signals are compared to monitor themechanical interconnection. In act 534, the first signal generated bythe first proximity sensor is compared with at least one of the firstconfiguration signal or the second configuration signal to monitor thefan nozzle drive system downstream of at least one of the first locationor the second location of the mechanical interconnection.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A nacelle for a turbofan engine comprising: anacelle forward portion that at least partially defines a bypass ductconfigured to transport bypass airflow of the engine, the nacelleforward portion having an aft edge that at least partially surrounds thebypass duct; a sleeve movably disposed aft of the nacelle forwardportion aft edge and having a trailing edge, the sleeve being movablerelative to the nacelle forward portion between a forward position andan aft position; a fan nozzle having a leading edge and a trailing edge,a primary flow exit for bypass airflow of the engine being partiallydefined by the fan nozzle trailing edge, the fan nozzle being movablydisposed behind the sleeve trailing edge and movable relative to thesleeve between a stowed position and a deployed position, the fan nozzlehaving a total range of motion relative to the nacelle forward portionbetween a forward-most position and an aft-most position, theforward-most position occurring when the sleeve is in the forwardposition and the fan nozzle is in the stowed position, the aft-mostposition occurring when the sleeve is in the aft position and the fannozzle is in the deployed position, the total range of relative motionbeing divided into a first portion and a second portion; and a firstproximity sensor attached to the nacelle forward portion and notattached to the fan nozzle, the first proximity sensor generating afirst signal that is indicative of when the fan nozzle is in the firstportion of the total range of relative motion and indicative of when thefan nozzle is not in the first portion of the total range of relativemotion.
 2. The nacelle of claim 1, wherein a variable area fan nozzle(VAFN) port is defined between the sleeve trailing edge and the fannozzle leading edge when the fan nozzle is in the deployed position, theVAFN port providing a flow exit for bypass airflow of the engine flowingthrough the bypass duct.
 3. The nacelle of claim 1, wherein a movementof the fan nozzle relative to the nacelle forward portion varies an exitarea of the primary flow exit.
 4. The nacelle of claim 1, wherein thefirst signal does not change in response to a change in the position ofthe fan nozzle within the second portion of the total range of relativemotion.
 5. The nacelle of claim 4, wherein the first proximity sensorincludes a first member and a second member that is movable relative tothe first member, the first member having a fixed position relative tothe nacelle forward portion and the second member interfacing with thefan nozzle only when the fan nozzle is disposed within the first portionof the total range of relative motion.
 6. The nacelle of claim 5,wherein the first proximity sensor includes a linear variabledifferential transformer in which the second member is biased into anextended position relative to the first member when the fan nozzle isnot disposed within the first portion of the total range of relativemotion.
 7. The nacelle of claim 4, wherein the first signal changes inresponse to a change in the position of the fan nozzle relative to thenacelle within the first portion of the total range of relative motion.8. The nacelle of claim 1, wherein the first proximity sensor isconfigured to accommodate variability in the position of theforward-most position relative to the nacelle forward portion.
 9. Thenacelle of claim 1, further comprising a second proximity sensorattached to the nacelle forward portion and not attached to the fannozzle, the second proximity sensor generating a second signal that isindicative of when the fan nozzle is in the first portion of the totalrange of relative motion and indicative of when the fan nozzle is not inthe first portion of the total range of relative motion.
 10. The nacelleof claim 9, including means to compare the first signal to the secondsignal.
 11. The nacelle of claim 1, further comprising: a slave linkmounted to the sleeve, the slave link being movable relative to thesleeve and interfacing with the fan nozzle only when the fan nozzle isdisposed within the first portion of the total range of relative motionso as to communicate a position of the fan nozzle to the first proximitysensor.
 12. The nacelle of claim 1, further comprising a slave linkassembly configured to be detachably mounted to the sleeve, the slavelink assembly including a slave plunger, a housing configured to bedetachably mounted to the sleeve, and a spring that biases the slaveplunger into an extended configuration relative to the housing absentcontact with the fan nozzle, the slave plunger interfacing with the fannozzle only when the fan nozzle is disposed within the first portion ofthe total range of relative motion so as to communicate a position ofthe fan nozzle to the first proximity sensor.
 13. The nacelle of claim1, wherein the first portion is less than 25% of the total range ofrelative motion.
 14. The nacelle of claim 9, further comprising: aplurality of fan nozzle actuators configured to selectively move the fannozzle relative to the sleeve between the stowed position and thedeployed position; a mechanical interconnection connecting a drivesource to the fan nozzle actuators to transfer an actuation motion fromthe drive source to the fan nozzle actuators, the drive source actuatingthe mechanical interconnection through a range of configurations betweena stowed configuration corresponding to the stowed position of the fannozzle and a deployed configuration corresponding to the deployedposition of the fan nozzle; a first configuration sensor generating afirst configuration signal indicative of the configuration of themechanical interconnection at a first location; a second configurationsensor generating a second configuration signal indicative of theconfiguration of the mechanical interconnection at a second location;and means to compare the first configuration signal to the secondconfiguration signal to monitor the mechanical interconnection.
 15. Thenacelle of claim 14, wherein the first and second configuration sensorseach includes a rotary variable differential transformer.
 16. A methodfor monitoring a movable fan nozzle of a turbofan engine, the methodcomprising: (a) during a first time period when the fan nozzle is in astowed position relative to a movable sleeve of the turbofan engine andthe movable sleeve is in a forward position relative to a nacelleforward portion of the turbofan engine, using a first proximity sensorto detect the presence of a first portion the fan nozzle, the firstproximity sensor being attached to the nacelle forward portion and notattached to the fan nozzle; (b) actuating a fan nozzle drive systemoperationally coupled with the fan nozzle to move the fan nozzlerelative to the sleeve from the stowed position to a deployed position;(c) actuating the fan nozzle drive system to return the fan nozzle fromthe deployed position to the stowed position; and (d) actuating a sleevedrive system operationally coupled with the sleeve to move the sleeveand the fan nozzle relative to the nacelle forward portion, wherein thesleeve moves from a forward position to an aft position relative to thenacelle forward portion; (e) actuating the sleeve drive system to returnthe sleeve from the aft position to the forward position; and (f) duringa second time period subsequent to (c) and (e), using the firstproximity sensor to detect the presence of the first portion of the fannozzle.
 17. The method of claim 16, wherein: (a) further comprises usinga second proximity sensor to detect the presence of a second portion ofthe fan nozzle, the second proximity sensor being attached to thenacelle forward portion and not attached to the fan nozzle; and (f)further comprises using the second proximity sensor to detect thepresence of the second portion of the fan nozzle.
 18. The method ofclaim 17, further comprising comparing a first signal generated by thefirst proximity sensor with a second signal generated by the secondproximity sensor to monitor for at least one of misalignment ordefective positioning of the fan nozzle.
 19. The method of claim 16,comprising: supporting a first member of the first proximity sensor in afixed position relative to the nacelle forward portion; using motion ofthe fan nozzle relative to the nacelle forward portion to articulate asecond member of the first proximity sensor relative to the first memberonly during a subset of a total range of relative motion between the fannozzle and the nacelle forward portion, the subset being less than 25%of the total range of relative motion; and generating a first signalindicative of a position of the second member relative to the firstmember.
 20. The method of claim 19, comprising using a slave linksupported by the sleeve to communicate a movement of the fan nozzle tothe second member.
 21. The method of claim 16, wherein each of (b) and(c) includes transferring an actuation motion from a drive sourcethrough a mechanical interconnection to a plurality of fan nozzleactuators operatively coupled with the fan nozzle.
 22. The method ofclaim 21, further comprising: generating a first configuration signalindicative of the configuration of the mechanical interconnection at afirst location; generating a second configuration signal indicative ofthe configuration of the mechanical interconnection at a secondlocation; and comparing the first and second configuration signals tomonitor the mechanical interconnection.
 23. The method of claim 22,further comprising comparing a first signal generated by the firstproximity sensor with at least one of the first configuration signal orthe second configuration signal to monitor the fan nozzle drive systemdownstream of at least one of the first location or the second location.